Turbo compressor and centrifugal chiller comprising same

The present disclosure relates to a turbo compressor and a centrifugal chiller including the turbo compressor.

In order to rotatably support a shaft that rotationally drives a compression mechanism, a contact-type bearing such as a rolling bearing is adopted in some cases in a turbo compressor. In this case, there is a concern over a complicated structure caused by providing a lubricant system of a bearing and a mechanical loss caused by friction of the bearing.

For this reason, in order to omit the lubricant system and reduce the mechanical loss, a magnetic bearing that is a non-contact type bearing is adopted in some cases instead of the rolling bearing.

As a structure of a fluid machine using the magnetic bearing, for example, there is a structure disclosed in FIG. 3 of PTL 1. In this structure, an auxiliary bearing and a displacement sensor are provided on both sides of the magnetic bearing along an axial direction of a shaft.

Patent Literature

[PTL 1] Japanese Unexamined Patent Application Publication No. 2002-218708

Technical Problem

However, in the structure disclosed in PTL 1, since the magnetic bearing, an auxiliary bearing, and the displacement sensor are provided to be separated from each other along the axial direction of the shaft, the components occupy a wide area in the axial direction. For this reason, it is necessary to design the shaft to be long, and there is a possibility that rotational vibration accompanying the rotation of the shaft occurs. In addition, there is a possibility that a size of the fluid machine increases.

The present disclosure is devised in view of such circumstances, and an object thereof is to provide a turbo compressor and a centrifugal chiller including the turbo compressor, which can shorten a length of a shaft in an axial direction, can suppress rotational vibration accompanying rotation of the shaft, and can realize miniaturization of the device.

Solution to Problem

In order to solve the problems, a turbo compressor and a centrifugal chiller including the turbo compressor according to the present disclosure adopt the following means.

According to one aspect of the present disclosure, there is provided a turbo compressor including a compression portion that compresses a refrigerant, a shaft that, drives the compression portion about a rotational axis, a magnetic bearing that is provided with an iron core portion on which a plurality of teeth are formed at an equal angular interval about the rotational axis and a plurality of coils which are wound around the plurality of teeth respectively and supports the inserted shaft in a non-contact manner, an auxiliary bearing that allows the shaft to be inserted thereinto, and a displacement sensor that detects a displacement of the shaft. The displacement sensor is provided between the coils adjacent to each other.

In the turbo compressor of the aspect, the displacement sensor is provided between the coils adjacent to each other. In the configuration, since the displacement sensor can be accommodated in the iron core portion of the magnetic bearing, a portion occupied by the components in an axial direction of the shaft can be reduced, for example, compared to a case where the magnetic bearing and the displacement sensor are provided to be separated from each other along the axial direction of the shaft. Accordingly, since a length of the shaft in the axial direction can be shortened or a distance between the magnetic bearings can be shortened, rotational vibration accompanying the rotation of the shaft is suppressed when using the turbo compressor. In addition, the miniaturization of the turbo compressor can be realized.

In the turbo compressor according to the aspect of the present disclosure, the auxiliary bearing is accommodated in a bearing box attached to the iron core portion.

In the configuration of the turbo compressor of the aspect, since the bearing box accommodating the auxiliary bearing is attached to the iron core portion of the magnetic bearing, a distance between the magnetic bearing and the auxiliary bearing can be shortened. Accordingly, the length of the shaft in the axial direction can be shortened or the distance between the magnetic bearings can be shortened.

In the turbo compressor according to the aspect of the present disclosure, the auxiliary bearing is accommodated in the bearing box formed of the same material as the iron core portion.

In the configuration of the turbo compressor of the aspect, since the iron core portion of the magnetic bearing and the bearing box accommodating the auxiliary bearing are formed of the same material, a change in a gap between the auxiliary bearing and the bearing box in a case where temperatures of the auxiliary bearing and the bearing box have changed can be suppressed, and the gap between the auxiliary bearing and the bearing box can be prevented from being deviated from a range of a specification plan value.

In the turbo compressor according to the aspect of the present disclosure, a cooling flow passage that allows a gas refrigerant to flow therethrough toward the displacement sensor is further included.

In the configuration of the turbo compressor of the aspect, the displacement sensor can be cooled by a gas refrigerant as the cooling flow passage causes the gas refrigerant to flow toward the displacement sensor. For this reason, even in a case where there is a possibility that the displacement sensor is thermally affected due to heat generation by the coils, a temperature rise of the displacement sensor can be suppressed, and an increase in a measurement error caused by the temperature rise of the displacement sensor can be prevented.

According to another aspect of the present disclosure, there is provided a centrifugal chiller including the turbo compressor, a condenser that condenses a refrigerant compressed by the turbo compressor, an expansion mechanism that expands the refrigerant condensed by the condenser, and an evaporator that evaporates the refrigerant expanded by the expansion mechanism.

Advantageous Effects of Invention

In the turbo compressor and the centrifugal chiller including the turbo compressor according to the present disclosure, the length of the shaft in the axial direction can be shortened, rotational vibration accompanying the rotation of the shaft can be suppressed, and the miniaturization of the device can be realized.

FIG. 1 is a diagram showing an example of a refrigerant circuit of a centrifugal chiller including a turbo compressor according to an embodiment of the present disclosure.

FIG. 2 is a vertical sectional view of the turbo compressor according to the embodiment of the present disclosure.

FIG. 3 is an enlarged view illustrating a structure around a magnetic bearing included in the turbo compressor according to the embodiment of the present disclosure.

FIG. 4 is a sectional view taken along cutting line I-I of FIG. 3 .

FIG. 5 is a sectional view taken along cutting line II-II of FIG. 3 .

FIG. 6 is a diagram showing another example of the refrigerant circuit of the centrifugal chiller including the turbo compressor according to the embodiment of the invention.

FIG. 7 is a vertical sectional view of a modification example of the turbo compressor according to the embodiment of the present disclosure.

FIG. 8 is a sectional view taken along cutting line III-III of FIG. 7 .

Hereinafter, a turbo compressor according to an embodiment of the present disclosure will be described.

As shown in FIG. 1 , a turbo compressor 1 is one of devices configuring a refrigerant circuit 3 of a centrifugal chiller. The refrigerant circuit 3 includes the turbo compressor 1 , a condenser 70 that condenses a refrigerant compressed by the turbo compressor 1 , an expansion valve 74 that expands the refrigerant condensed by the condenser 70 , and an evaporator 76 that evaporates the refrigerant expanded by the expansion valve 74 . The turbo compressor 1 is a turbo compressor that compresses a low-pressure gas refrigerant evaporated by the evaporator 76 to make into a high-temperature and high-pressure gas refrigerant.

As illustrated in FIG. 2 , the turbo compressor 1 is configured to include a casing 10 that forms an outer shell thereof, a compression portion 12 that has a plurality of impellers 12 A, an electric motor 14 , a shaft 15 , and radial magnetic bearings (magnetic bearings) 30 A and 30 B, a plurality of auxiliary bearings 40 , a thrust magnetic bearing 44 , and displacement sensors 50 .

The inside of the casing 10 is partitioned into an electric motor chamber 11 A and a compression chamber 11 B by a partition wall 10 A.

The electric motor chamber 11 A accommodates the electric motor 14 , the radial magnetic bearings 30 A and 30 B, the auxiliary bearings 40 , the displacement sensors 50 , and the thrust magnetic bearing 44 .

The compression chamber 11 B accommodates the compression, portion 12 having the plurality of impellers 12 A.

In addition, the shaft 15 extends in a rotational axis X direction (a right-and-left direction shown in FIG. 2 ), and are accommodated in the casing 10 across the electric motor chamber 11 A and the compression chamber 11 B by penetrating the partition wall 10 A.

The electric motor 14 is configured to include a stator 14 A that is fixed to an inner peripheral surface of the casing 10 and a rotor 14 B that is fixed to an outer peripheral surface of the shaft 15 and rotates about a rotational axis X on an inner peripheral side of the stator 14 A.

As described above, the shaft 15 is provided across the electric motor chamber 11 A and the compression chamber 11 B by penetrating the partition wall 10 A, and one end thereof projects to a compression chamber 11 B side. Further, the compression portion 12 is configured such that the plurality of impellers 12 A are attached to the one end on the compression chamber 11 B side to integrally rotate about the rotational axis X.

Out of the radial magnetic bearings 30 A and 30 B, the radial magnetic bearing 30 B is disposed between the electric motor 14 and the partition wall 10 A, and the radial magnetic bearing 30 A is disposed on an opposite side to the radial magnetic bearing 30 B with respect to the electric motor 14 . In addition, the radial magnetic bearings 30 A and 30 B are fixed and supported with respect to the casing 10 by being supported by magnetic bearing support structures 20 A and 20 B respectively, which are connected to the casing 10 . By energizing the radial magnetic bearings 30 A and 30 B, the radial magnetic bearings 30 A and 30 B support the shaft 15 so as to be rotatable about the rotational axis X in a non-contact manner. In addition, the thrust magnetic bearing 44 is provided to sandwich a disk-shaped thrust plate provided at the other end of the shaft 15 (an end portion on an opposite side to the compression portion 12 ), and restricts movement of the shaft 15 in the rotational axis X direction in a non-contact manner.

In addition to the radial magnetic bearings 30 A and 30 B, the plurality of auxiliary bearings 40 are provided.

The auxiliary bearings 40 are so-called touchdown bearings that, support the shaft 15 instead of the radial magnetic bearings 30 A and 30 B and the thrust magnetic bearing 44 which have lost a non-contact supporting function when the energization of the radial magnetic bearings 30 A and 30 B and the thrust magnetic bearing 44 is stopped.

When the shaft 15 is supported in a non-contact manner by the radial magnetic bearings 30 A and 30 B and the thrust magnetic bearing 44 , the auxiliary bearings 40 are also not in contact with the shaft 15 . At this time, a bearing clearance between the auxiliary bearings 40 and the shaft 15 is set to be smaller than a bearing clearance between the radial magnetic bearing 30 A or 30 B and the shaft 15 . Accordingly, even when the shaft 15 is supported by the auxiliary bearings 40 instead of the radial magnetic bearings 30 A and 30 B and the thrust magnetic bearing 44 , the bearing clearance between the radial magnetic bearing 30 A or 30 B and the shaft 15 and the bearing clearance between the thrust magnetic bearing 44 and the shaft remain. Thus, damage to the radial magnetic bearings 30 A and 30 B and the thrust magnetic bearing 44 is avoided.

In addition, the casing 10 accommodates the displacement sensors 50 that measure a displacement of the shaft 25 in a radial direction, and the vibration of the rotating shaft 15 is monitored.

Next, a structure of the radial magnetic bearing 30 A, the disposition of the displacement sensors 50 , and a support structure of the auxiliary bearing 40 will be described.

As illustrated in FIG. 3 , the radial magnetic bearing 30 A is configured to include a lay-up steel panel-shaped iron core portion 32 and coils 36 . As illustrated in FIG. 4 , the shaft 15 is inserted on the inner peripheral side of the iron core portion 32 . In addition, on the inner peripheral side of the iron core portion 32 , a plurality of teeth 34 are formed at equal angular intervals about the rotational axis X of the inserted shaft 15 . Although the six teeth 34 are formed in FIG. 4 , the number is not limited to six. The number may be five or less, or may be seven or more.

The coil 36 is wound around each of the teeth 34 . A magnetic force is generated in the teeth 34 as the coils 36 are energized, and the shaft 15 is supported by the magnetic force in a non-contact manner.

In the radial magnetic bearing 30 A of the turbo compressor 1 of the embodiment, the displacement sensor 50 is provided between the coils 36 adjacent to each other. In view of the fact that a space is generated between the coils 36 adjacent to each other in a circumferential direction, the radial magnetic bearing accommodates the displacement sensor 50 in the space. That is, the displacement sensor 50 is accommodated without protruding from the iron core portion 32 in the rotational axis X direction of the shaft 15 (refer to FIG. 2 ).

As illustrated in FIG. 3 , the auxiliary bearings 40 each are provided such that an outer peripheral surface of an outer ring thereof is attached to the iron core portion 32 and is fitted to an inner peripheral surface of a thick cylindrical bearing box 42 which extends along the rotational axis X. As described above, the shaft 15 is inserted in the auxiliary bearings 40 with a predetermined bearing clearance provided with respect to the auxiliary bearings 40 (refer to FIG. 5 ).

Although the two auxiliary bearings 40 are provided in the bearing box 42 in FIG. 3 , the number is not limited to two. The number may be one, or may be three or more.

The bearing box 42 and the iron core portion 32 are fixed by a fastening member 52 . The fastening member 52 is a rod-shaped member that penetrates the bearing box 42 and the iron core portion 32 and extends in the rotational axis X direction. The fastening member 52 is, for example, a rivet. Although eight rivets are fixed in FIGS. 4 and 5 , the number is not limited to eight. The number may be seven or less, or may be nine or more. The bearing box 42 may be made of the same material as the iron core portion 32 .

Although the radial magnetic bearing 30 A and a structure around the radial magnetic bearing have been described hereinbefore, also the radial magnetic bearing 30 B has the same structure as the radial magnetic bearing 30 A. Thus, description thereof will be omitted herein.

Next, cooling flow passages 22 A and 22 B illustrated in FIG. 2 will be described.

As mechanisms for cooling the displacement sensor 50 toward the displacement sensor 50 provided between the coils 36 adjacent to each other, the cooling flow passages 22 A and 22 B illustrated in FIG. 2 are provided in the turbo compressor 1 of the embodiment.

The cooling flow passages 22 A and 22 B are thin and long flow passages formed across the casing 10 and the magnetic bearing support structures 20 A and 20 B. One end of each of the cooling flow passages 22 A and 22 B on a casing 10 side communicates with an outside of the casing 10 (the turbo compressor 1 ). In addition, the other end of each of the cooling flow passages 22 A and 22 B is formed to face the displacement sensor 50 . By supplying a cooling gas from the outside to the one end of each of the cooling flow passages 22 A and 22 B, the cooling gas can be jetted from the other end of each of the cooling flow passages 22 A and 22 B toward a surface of the displacement sensor 50 which is accommodated in each of the radial magnetic bearings 30 A and 30 B via the cooling flow passages 22 A and 22 B, the surface being a surface intersecting the rotational axis X direction, more specifically, a surface orthogonal to the rotational axis X direction.

As shown in FIG. 1 , the cooling gas supplied to the one end of each of the cooling flow passages 22 A and 22 B can set a gas phase portion of the condenser 70 that configures the refrigerant circuit 3 of the centrifugal chiller in which the turbo compressor 1 is provided as a supply source. The cooling gas taken out from the gas phase portion of the condenser 70 is guided to the cooling flow passages 22 A and 22 B via a supply path 24 .

As shown in FIG. 6 , the cooling gas supplied to one end of each of the cooling flow passages 22 A and 22 B may set a gas phase portion of an economizer 72 that configures a refrigerant circuit 3 ′ of the centrifugal chiller in which the turbo compressor 1 is provided as a supply source. The cooling gas taken out from the gas phase portion of the economizer 72 is guided to the cooling flow passages 22 A and 22 B via a supply path 24 ′.

As modification examples of the cooling flow passages 22 A and 22 B, cooling flow passages 22 A′ and 22 B′ illustrated in FIG. 7 may be formed. The cooling flow passages 22 A′ and 22 B′ can not only jet the cooling gas toward the surfaces of the displacement sensors 50 intersecting the rotational axis X direction, more specifically, the surfaces orthogonal to the rotational axis X direction just as the cooling flow passages 22 A and 22 B (refer to FIG. 2 ) but also can jet the cooling gas toward a surface on an opposite side to surfaces of the displacement sensors 50 facing the shaft 15 , that is, toward the inner peripheral side from an outer peripheral side of the iron core portion 32 , as illustrated in FIG. 8 .

The cooling flow passages 22 A, 22 B, 22 A′, and 22 B′ shown in FIGS. 2 and 7 are merely examples, and may be flow passages that are configured such that a cooling gas can flow from the outside of the turbo compressor 1 to the displacement sensors 50 .

The embodiment has the following effects.

The displacement sensor 50 is provided between the coils 36 adjacent to each other. In the configuration, since the displacement sensors 50 can be accommodated inside the iron core portion 32 , a portion occupied by the components in the rotational axis X direction of the shaft 15 can be reduced, for example, compared to a case where the radial magnetic bearings 30 A and 30 B and the displacement sensors 50 are provided to be separated from each other along the rotational axis X direction of the shaft 15 . Accordingly, since a length of the shaft 15 in the rotational axis X direction can be shortened or a distance between the radial magnetic bearing 30 A and the radial magnetic bearing 30 B can be shortened, rotational vibration accompanying the rotation of the shaft 15 is suppressed when the turbo compressor 1 is operated. In addition, the miniaturization of the turbo compressor 1 can be realized.

In addition, since the bearing box 42 accommodating the auxiliary bearings 40 is attached to the iron core portion 32 of each of the radial magnetic bearings 30 A and 30 B, a distance between the radial magnetic bearing 30 A or 30 B and the auxiliary bearing 40 can be shortened. Accordingly, the length of the shaft 15 in the rotational axis X direction can be shortened or the distance between the radial magnetic bearing 30 A and the radial magnetic bearing 30 B can be shortened.

In addition, the displacement sensors 50 can be cooled by a gas refrigerant by jetting the gas refrigerant toward the displacement sensors 50 via the cooling flow passages 22 A, 22 B, 22 A′, and 22 B′. For this reason, even in a case where there is a possibility that the displacement sensors 50 are thermally affected due to heat generation by the coils 36 , temperature rises of the displacement sensor 50 can be suppressed, and an increase in a measurement error caused by the temperature rises of the displacement sensors 50 can be prevented.

1 turbo compressor

3 , 3 ′ refrigerant circuit

10 casing

11 A partition wall

11 A electric motor chamber

11 B compression chamber

12 compression portion

12 A impeller

14 electric motor

14 A stator

14 B rotor

15 shaft

20 A, 20 B magnetic bearing support structure

22 A, 22 B, 22 A′, 22 B′ cooling flow passage

30 A, 30 B radial magnetic bearing (magnetic bearing)

32 iron core portion

34 teeth

36 coil

40 auxiliary bearing

42 bearing box

44 thrust magnetic bearing

50 displacement sensor

52 fastening member

X rotational axis